The present invention relates to an apparatus for supporting a variable number of objects, such as books, CDs or the like, on a shelf unit. In particular, the apparatus includes two or more relatively movable members comprising opposed surface defining planes of support biased toward one another to support the variable number of objects therebetween.
Although numerous relatively movable biased bookends are known in the art, there are problems with existing structures. Shelving comes in several lengths, varying from a foot in length to ten or more feet. Known spring-loaded bookends have a fairly limited travel distance and are not capable of the degree of travel flexibility necessary to accommodate use with large shelves. In any shelf, two extreme conditions could occur: the shelf could be nearly full of books or it could be nearly empty. As the length of the shelf increases, so must the travel of the bookend if these extreme conditions are to be met. Known spring-loaded bookends are not capable of meeting these conditions for long book shelves and oftentimes not even for short shelves. A reason for this is in the spring element used. Tension/compression springs have a large dead space in order to provide a low change in force constant. That is, they must have a large number of coils, which occupy a large area of space when contracted. Thus, with such a construction, it is difficult to accommodate a very small number of books due to the dead space and difficult to accommodate a large number of books with the spring fully extended because maintaining the spring extended for long periods of time can result in spring fatigue and failure.
Another problem with spring-loaded bookends is a clearance problem associated with some shelving. Often shelving is sized to accommodate a certain size of book. Although some shelving may allow greater tolerances, other shelving has small tolerances in dimensions such as overall height between shelves, or in shelf depth relative to the size of books being shelved. As such, an add-on bookend needs to have small dimensions to allow use of the largest possible height and number of books or other objects being supported. However, some bookends fail to accomplish this.
Additionally, known spring-loaded bookends have no structure provided that can control, stop or govern the amount of force applied. Tension/compression springs have varying force based on the amount of extension due to the non-linear nature inherent in such springs. Moreover, known bookends have no mechanisms provided to govern or control the rate/time of return travel. As such, known adjustable, spring-loaded bookends can be awkward or even unsafe to operate due to rapid retraction. Additionally, some bookends have inconsistent retraction due to varying application force caused by use of a non-linear spring force that applies more force at some positions of extension/retraction than other positions (i.e., more or less force is applied at extreme end positions than intermediate positions).
Moreover, while some bookends have end stops that define the ends of travel, known spring-loaded bookends are not capable of adjustably locking the bookend at intermediate positions, such as to facilitate easy book removal or addition.
A particular known bookend is the Bookworm.TM. made by Helix, Ltd. of England. This bookend consists of one L-shaped member riveted to a constant force spring with a large diameter. The bookend is placed on a horizontal surface and contains one or a few books or other objects between the L-shaped member and the large diameter coil. However, several problems still exist with such a device. First, the device cannot accommodate a large number of books as an unfixed structure like this is increasingly unstable the larger the extension. Second, the large diameter coil takes up a substantial amount of space, thus reducing the capacity of the shelf unit. Third, as the spring itself serves as a support surface, the Bookworm.TM. is limited to use with objects having a limited range of heights, as taller or shorter ones may not be adequately supported by the coil of the spring. Moreover, as the constant force spring is unwound, the effective height of the end support is reduced. Fourth, the bookworm is difficult to operate as both hands are necessary to extend the structure to add additional objects. Fifth, the Bookworm is provided as a support structure with wide dimensions to contain books, etc. within its own structure by closing gaps on itself and is not concerned with use in conjunction with an existing bookshelf.
There is a need for an adjustable apparatus that can support a variable number of objects, such as books, and overcome the deficiencies of the prior art.